UBC researchers help find 15,000 candidate cosmic magnifying glasses in Euclid data

Before the Euclid space telescope began scanning the sky, astronomers had confirmed fewer than a thousand strong gravitational lenses. Now they have about 15,000 new candidates, according to Hrishabh Srivastava, a doctoral student in UBC's department of physics and astronomy and a co-author of the research.

Strong gravitational lenses occur when the gravity of a foreground galaxy bends the light of objects far behind it, acting like a cosmic magnifying glass. UBC says the new catalogue is larger than all earlier collections of strong lenses combined, and that its researchers helped uncover it. The work puts a Vancouver university inside one of the biggest efforts yet to study the parts of the universe that can't be seen directly: dark energy and dark matter, which together make up about 95 per cent of it.

Srivastava said the odds of finding a strong lens are about one in 10,000.

The candidates emerged from the first major data release from Euclid, the European Space Agency's space telescope, which launched in 2023. The release comprises 1.7 million gigabytes of data from 13 months of observation and covers almost five per cent of the night sky. It includes spectra from more than 160 million sources. Because Euclid operates above Earth's atmosphere, it can pick out faint, distant features that would otherwise be hard to detect.

A global consortium of more than 2,000 scientists, including more than 30 Canadians, analysed the data. Their work revealed more than 900 million galaxies and 60 million quasars. The findings are described in 26 papers submitted to the journal Astronomy & Astrophysics. Canadian organizations involved include UBC and the University of Waterloo, among others.

The 15,000 lenses are candidates, not confirmed discoveries. Finding them took a four-part process: machine-learning software made the first pass, citizen scientists and then experts checked what it flagged, and final verification relies on follow-up data from other telescopes.

There is much more data to come. The current release covers about 14 per cent of the sky area Euclid will survey over its six years of service, and the mission aims to map more than one-third of the sky to build a three-dimensional map of the universe. Srivastava will attempt to estimate the dark matter distribution of the universe.